Looks like i broke a rule by creating a new account and asking about the recovery of my main account. Sorry about that, but i did not see any other option how to proceed.
Yes, i still have access to the mail address of my main account.
I'm using "GMX", which is a european provider. As i said, the mail for account name recovery was received after a few seconds, but i was never even able to send a password recovery mail, because i got the error from the very first try.